EP2794989B1 - Sheet of wrinkle-resistant paper - Google Patents

Description

The invention relates to a sheet of paper resistant to crumpling and its method of manufacture. For the purposes of the invention "wrinkle-resistant" means that the sheet has, following wrinkling, a low crease marking.

Since banknotes are exposed during their lifetime to many manipulations, it is constantly sought to improve their durability and for these purposes in particular to strengthen their mechanical strength.

In general, it is found that in view of many manipulations, the bank notes have a crumpled and / or folded appearance. However, wrinkled areas have deep folds, irreversible, which in time often give rise to tears. Thus, the presence of folds weakens and reduces the life of bank notes. In addition, the presence of folds, makes the automated processing of these bank notes difficult, for example during verifications of authenticity or wear on sorting machine.

In particular on substrates provided with a "barrier" layer, in particular banknotes, these wrinkled zones give rise to embrittlement of said "barrier" layer allowing the penetration of "soils".

By "barrier layer" is meant a layer blocking the pores of the substrate considered, for example a sheet of paper, and dedicated to confer on this support enhanced protection. This layer may be hydrophobic and / or oleophobic.

By "soiling" is meant in particular aqueous or oleaginous liquids, or even sub-millimeter particles, and mixtures thereof.

A first wrinkle resistance gain regarding the maintenance of zero porosity after creasing was achieved via incorporation into the cellulosic material dedicated to forming the safety document of a flocculated latex. As described in the document FR 2 916 768 , the latex is flocculated in the interstices of the fibrous mat thus conferring on it a localized elasticity and thus a gain in resilience.

However, it would be advantageous to be able to reinforce this crease resistance by improving other characteristics and in particular by decreasing the crease marking.

According to one of its aspects, the present invention therefore aims to provide a security document based on cellulosic fibers which has a resistance to wrinkling enhanced both in terms of resilience and crease marking.

According to another of its aspects, the object of the present invention is to provide a security document based on cellulosic fibers whose mechanical properties are not altered by the treatment aimed at reinforcing their resistance to wrinkling.

According to yet another of its aspects, the object of the present invention is to provide a security document capable of satisfactorily satisfying all paper manufacturing constraints.

Thus, according to one of its aspects, the invention relates to a sheet of paper with a high resistance to wrinkling and folding, in particular for the production of banknotes, comprising a fibrous substrate impregnated with the core by at least one hydroxyl polymeric binder characterized in that said binder and the fibers of said substrate are at least partially covalently bound to at least one siloxane derivative.

By "core impregnation" is meant that the hydroxyl polymeric binder is established deep in the substrate and is found on the surface as well. Thus, the fibers of the substrate are essentially in contact with the hydroxylated polymeric binder.

According to a variant, said fibrous substrate is also impregnated to the core by at least one siloxane derivative.

Certainly, the publication of Noureddine Abidi et al. (Textile Journal Research, Vol 77 (9): 668-674 ) already proposes to impregnate woven supports such as fabrics with vinylmethoxysilane in order to increase their resistance to wrinkling.

However, as is apparent from the examples below, the treatment of a paper-like fibrous substrate with only a silanol derivative under the conditions recommended in this document proves detrimental to the mechanical properties of the paper support thus obtained.

Surprisingly, the inventors have found that, on the other hand, the use of silanol in combination with a hydroxylated polymeric binder in the image of polyvinyl alcohol (PVA) makes it possible to overcome this significant decrease in mechanical strength.

Advantageously, and as is apparent from the examples below, the sheets of paper according to the invention show, against all expectations, good resistance to wrinkling both in terms of resilience and crease marking, without altering its mechanical characteristics.

1. (i) l'imprégnation dudit substrat avec une solution aqueuse d'un liant polymérique hydroxylé notamment en une proportion variant de 1 à 10 % en poids sec par rapport au poids des fibres en sec,
2. (ii) l'imprégnation dudit substrat avec une solution aqueuse d'au moins un dérivé silanol, et
3. (iii) le séchage du substrat modifié selon les étapes (i) et (ii),

The invention also relates, in another of its aspects, to a method of manufacturing a sheet of paper with high resistance to wrinkling and folding, in particular for the manufacture of banknotes as described above, from a fibrous substrate comprising

1. (i) impregnating said substrate with an aqueous solution of a hydroxyl polymeric binder, especially in a proportion ranging from 1 to 10% by dry weight relative to the weight of the dry fibers,
2. (ii) impregnating said substrate with an aqueous solution of at least one silanol derivative, and
3. (iii) drying the modified substrate according to steps (i) and (ii),

step (ii) can be performed beforehand, simultaneously or consecutively to step (i).

Preferably step (ii) is performed simultaneously or consecutively to step (i).

According to another of its aspects, the present invention relates to a multilayer structure comprising a sheet of paper as described above.

Thus, a multilayer structure may be formed of a superposition of several layers of identical or different chemical nature with at least one of them being represented by a sheet of paper according to the invention.

For example, it may be a structure formed of a sheet of paper according to the invention, the latter being coated on one of its outer faces or both, a plastic film.

According to yet another of its aspects, the invention relates to the use of a silanol derivative as an insolubilization agent in the paper industry. An insolubilization agent makes it possible to avoid the solubilization of the hydroxylated polymer present in the paper during a long-term contact with an aqueous solution (water). This agent consists of reactive chemical functions, when subjected to thermal energy, with the hydroxyl functions of the hydroxylated polymer.

According to yet another of its aspects, the invention relates to the use of a silanol derivative as a sizing agent in the paper industry. A bonding agent is used to provide hydrophobicity to the treated fibrous substrate in order to improve the repulsion by the substrate of the aqueous solutions (water) brought into contact with it.

Unexpectedly, the inventors have indeed found that the silanol derivatives in particular as defined below prove to be effective in increasing the insolubilization of the hydroxylated polymeric binder while permitting the production of a sheet of paper resistant to water. 'water. The inventors have also found that the insolubilization with the silanol derivatives is particularly increased when step (ii) of the process defined below, is carried out simultaneously or consecutively to step (i).

Furthermore, these silanol derivatives are advantageously free of undesirable effects, particularly in terms of toxicity, in contrast to polyamide-epichlorohydrin or polyamine-amide-epichlorohydrin resins conventionally considered for this function in the paper industry.

SILOXANE DERIVATIVE

As specified above, within the meaning of the invention, a siloxane derivative covers any compound comprising at least one silicon atom bonded to at least one oxygen atom. They are obtained from silanol derivatives according to the invention which have reacted with fibers, other silanol derivatives and / or the hydroxylated polymeric binder.

With regard specifically to the presence of siloxane derivatives linked at least in part to the hydroxylated polymeric binder and to the fibers constituting it, the paper sheet according to the invention has infrared absorption bands characteristic of the CO-Si bonds in which C originates from cellulose or a hydroxyl polymeric binder. These bands are respectively observed between 1100 cm ^-1 and 1250 cm ^-1 .

dans laquelle :

• □ représente une liaison covalente avec une fibre, un autre atome de silicium ou le liant polymérique hydroxylé,
• A représente un groupement hydrocarboné divalent, saturé ou non, la chaîne hydrocarbonée peut être le cas échéant interrompue par un ou plusieurs atome(s) d'azote, d'oxygène, de soufre ou de phosphore, et substituée par un ou plusieurs groupement(s) hydrocarbonés comprenant un ou plusieurs atome(s) d'azote, d'oxygène, de soufre, de phosphore et d'halogène en particulier de fluor et/ou par un ou plusieurs groupement(s) cyclique(s) en C3 à C6 ou aromatique(s) et dont la chaîne hydrocarbonée peut être le cas échéant interrompue par un ou plusieurs atome(s) d'azote, d'oxygène de soufre ou de phosphore,
• B représente
  • une liaison -O-□, ou
  • un halogène, ou
  • un groupement hydrocarboné, saturé ou non, linéaire ou ramifié ou cyclique, possédant ou non un ou plusieurs groupe(s) cyclique(s) et dont la chaîne hydrocarbonée peut être interrompue par un ou plusieurs atome(s) d'azote, d'oxygène ou de soufre,
• R représente
  • un atome d'hydrogène,
  • un atome d'halogène et de préférence de fluor, ou
  • un motif de formule (II)
    
    dans laquelle B' représente
    • une liaison -O-□ ou
    • un halogène, ou
    • un groupement hydrocarboné, saturé ou non, linéaire ou ramifié ou cyclique, possédant ou non un ou plusieurs groupe(s) cyclique(s) et dont la chaîne hydrocarbonée peut être interrompue par un ou plusieurs atome(s) d'azote, d'oxygène ou de soufre.

Advantageously, in the context of the invention, this siloxane derivative corresponds to formula (I)

in which :

• Represents a covalent bond with a fiber, another silicon atom or the hydroxylated polymeric binder,
• A represents a divalent hydrocarbon group, saturated or not, the hydrocarbon chain may optionally be interrupted by one or more nitrogen atom (s), oxygen, sulfur or phosphorus, and substituted with one or more groups ( s) hydrocarbon compounds comprising one or more nitrogen, oxygen, sulfur, phosphorus and halogen atoms, in particular fluorine atoms and / or by one or more C3 cyclic group (s) at C6 or aromatic (s) and whose hydrocarbon chain may be optionally interrupted by one or more atom (s) of nitrogen, sulfur or phosphorus oxygen,
• B represents
  • a -O- □ link, or
  • a halogen, or
  • a hydrocarbon group, saturated or unsaturated, linear or branched or cyclic, with or without one or more cyclic group (s) and whose hydrocarbon chain can be interrupted by one or more nitrogen atom (s), oxygen or sulfur,
• R represents
  • a hydrogen atom,
  • a halogen atom and preferably a fluorine atom, or
  • a pattern of formula (II)
    
    in which B 'represents
    • a -O- □ or
    • a halogen, or
    • a hydrocarbon group, saturated or unsaturated, linear or branched or cyclic, with or without one or more cyclic group (s) and whose hydrocarbon chain can be interrupted by one or more nitrogen atom (s), oxygen or sulfur.

For the purposes of the present invention, the term "hydrocarbon group" or "hydrocarbon chain" more particularly denotes a linear or branched C1 to C30, especially C1 to C18, group.

According to a first preferred embodiment, B represents a bond -O- □ and R represents a hydrogen or fluorine atom in formula I of siloxane derivative.

In this embodiment, A preferably represents a saturated or unsaturated divalent hydrocarbon group, the hydrocarbon chain being interrupted by one or more oxygen atom (s), optionally substituted with an epoxide group.

dans laquelle R' représente un motif -CH=CH₂ ou une chaîne hydrocarbonée, le cas échéant substituée avec un ou plusieurs atome(s) de fluor, un groupement époxyde ou une chaîne hydrocarbonée interrompue par un ou plusieurs atome(s) d'oxygène et fonctionnalisée avec un groupement époxyde.By way of non-limiting illustration of these siloxane derivatives, the following derivatives can in particular be cited:

in which R 'represents a -CH = CH _{2 unit} or a hydrocarbon-based chain, optionally substituted with one or more fluorine atoms, an epoxide group or a hydrocarbon chain interrupted by one or more atom (s) of oxygen and functionalized with an epoxide group.

According to a second preferred embodiment, R represents the unit of formula (II) as described above, and B and B 'represent a bond -O- □. In this embodiment, A advantageously comprises one or more nitrogen atom (s) and / or oxygen atom (s).

avec n variant de 2 à 10 et de préférence de 2 à 7

avec □ représentant une liaison covalente avec une fibre, un autre atome de silicium ou le liant polymérique hydroxylé.By way of non-limiting illustration, the siloxane derivatives present in the fibrous substrate of the paper sheet according to the invention may in particular be cited as follows:

with n varying from 2 to 10 and preferably from 2 to 7

with □ representing a covalent bond with a fiber, another silicon atom or the hydroxylated polymeric binder.

• un halogène, ou
• un groupement hydrocarboné monovalent, saturé ou non, linéaire ou ramifié ou cyclique, possédant ou non un ou plusieurs groupe(s) cyclique(s) et dont la chaîne hydrocarbonée peut être interrompue par un ou plusieurs atome(s) d'azote, d'oxygène ou de soufre.

According to a third preferred embodiment, R represents the unit of formula (II) as described above, and B and B 'represent:

• a halogen, or
• a monovalent hydrocarbon group, saturated or unsaturated, linear or branched or cyclic, with or without one or more cyclic group (s) and whose hydrocarbon chain can be interrupted by one or more nitrogen atom (s), oxygen or sulfur.

In this embodiment, A advantageously comprises one or more nitrogen atom (s) and / or oxygen atom (s).

avec n variant de 2 à 10 et de préférence de 2 à 7

avec □ représentant une liaison covalente avec une fibre, un autre atome de silicium ou le liant polymérique hydroxylé.By way of illustration and without limitation, such siloxane derivatives may in particular be cited as the following derivatives:

with n varying from 2 to 10 and preferably from 2 to 7

with □ representing a covalent bond with a fiber, another silicon atom or the hydroxylated polymeric binder.

The siloxane derivative may be present in the fibrous substrate in a proportion ranging from 5 to 30% and in particular from 10 to 20% by dry weight relative to the total weight of the fibers in dry form.

The siloxane derivative may be present in the fibrous substrate in a proportion ranging from 100 to 350% and in particular from 200 to 300% by dry weight relative to the total weight of hydroxylated polymeric binder.

POLYMERIOUE HYDROXYL BOND

The hydroxyl polymeric binder according to the invention comprises at least one hydroxyl group, and advantageously more than one hydroxyl group.

The hydroxylated polymeric binder impregnating the substrate is preferably based on polyvinyl alcohol (PVA), starch, pullulan, polyhydroxyalkyl methacrylate, polyglycerol monomethacrylate or a polysaccharide.

Preferably, it is based on PVA.

Said hydroxylated polymeric binder is in a proportion ranging from 1 to 10% by dry weight relative to the total weight of the fibers in dry.

The compound considered to form the polymeric binder is generally contacted with the fibrous substrate in the form of an aqueous preparation, preferably in line on the paper machine, preferably with the aid of an impregnator and / or a surfacing device.

The polyvinyl alcohol may for example be dissolved in water at a level of 1% to 10% by weight, preferably between 3% and 6%, before impregnation of the paper substrate.

To apply the aqueous PVA preparation can be used an impregnator and / or an in-line surfacing device, including in particular predosage rollers, engraved rollers, transfer rollers before dosing output.

Another alternative may be to soak the fibrous substrate in an aqueous bath containing the compound for forming the polymeric binder.

Where appropriate, the aqueous solution containing this hydroxyl polymeric binder may be further supplemented with other additives usually used in the paper industry.

FIBROUS SUBSTRATE

The substrate useful for the implementation of the present invention may be any paper or nonwoven suitable for making paper and more particularly security documents like banknotes.

This includes nonwoven fibrous papers, including natural fibers, in particular cellulosic fibers or synthetic fibers, or a mixture of natural and synthetic fibers.

In particular, said fibers may be cellulosic fibers mixed with synthetic fibers.

Among the natural fibers, mention may be made of wood fibers, for example of hardwood, softwood or their mixture, of eucalyptus, cotton, bamboo, viscose, straw, abaca, asperto, hemp , jute, flax, sisal or mixtures thereof.

The fibers may be bleached, semi-bleached or unbleached.

Among the synthetic fibers, mention may be made of polyester, polyamide, rayon and viscose fibers.

The fibers can be short or long.

The fibers may have an average length ranging from 0.1 to 30 mm, in particular from 1 to 15 mm.

According to one embodiment of the invention, the fibrous substrate may for example consist solely of cellulosic fibers.

Preferably, according to another embodiment of the invention, the fibers used in the composition of the sheet may comprise synthetic fibers. This embodiment is particularly advantageous because it makes it possible to further improve the tear-resistance properties of the sheet according to the invention.

In particular, the paper sheets according to the invention comprising synthetic fibers have a tear strength greater than 1300 mN.

According to a sub-mode of this embodiment of the invention, the synthetic fibers are in a proportion ranging from 5 to 30% by dry weight relative to the total weight of the fibers.

According to another sub-mode of this embodiment of the invention, the sheet comprises cotton fibers in a proportion of at least 70% by dry weight relative to the total weight of the fibers and synthetic fibers in a proportion varying from 10 to 30% by dry weight relative to the total weight of the fibers, the sum total of cotton fibers and synthetic fibers being equal to 100%.

According to yet another sub-mode of this embodiment of the invention, said synthetic fibers are selected from polyamide fibers and / or polyester fibers. It may be, for example, polyamide 6-6 fibers or polyester fibers sold by the company Kuraray under the trade name EP 133.

According to the invention, the fibrous substrate may for example consist of cellulosic fibers and synthetic fibers of polyamide 6-6, advantageously in a proportion of 90% by weight of cellulosic fibers relative to the total weight of dry fibers.

According to yet another embodiment of the invention, the fibrous substrate according to the invention may further comprise a flocculated latex in particular in a proportion ranging from 6 to 50% by weight relative to the total weight of dry fibers, advantageously in a proportion of 10% by weight relative to the total weight of dry fibers.

The sheets of paper according to the invention, comprising such a flocculated latex may be prepared according to the patent FR 2 916 768 .

The fibrous substrate may have, as finished and dry paper, before treatment according to the invention, a grammage of between 20 and 120 g / m ² and a thickness ranging from 30 to 180 microns.

According to an alternative embodiment, the fibrous substrate considered according to the invention may comprise one or more watermark (s) and / or one or more security element (s).

Among the security elements that can be incorporated in the fibrous substrate, some are detectable to the eye, daylight or artificial light, without the use of a particular device. These security elements comprise for example colored fibers or boards, fully or partially printed or metallized wires. These security elements are called first level.

Other types of additional security elements are detectable only with a relatively simple apparatus, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These security elements comprise, for example, fibers, boards, strips, wires or particles. These security elements may be visible to the naked eye or not, being for example luminescent under a lighting of a Wood lamp emitting in a wavelength of 365 nm. These security elements are said to be second level.

Other types of security elements require for their detection a more sophisticated detection device. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. The automatic detection of the signal makes it possible to authenticate, if necessary, the document. These security elements comprise, for example, tracers in the form of active materials, particles or fibers capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are said to be third level.

Thus, according to a preferred embodiment of the invention, the sheet of paper as described above is a security document.

By way of non-limiting illustration of the security documents falling within the scope of the present invention, mention may in particular be made of a passport, an identity card, a means of payment, in particular a bank note, a gift certificate or a security certificate. purchase, a check, a voucher, a credit card, a ticket to sports events or a certificate of authenticity. A security document according to the invention may also include a booklet.

Preferably, a security document according to the invention is a bank note.

The fibrous substrate can be obtained beforehand on an inclined table, "to form", flat table (Fourdrinier) or round form or any other tool capable of forming a sheet of fibers from their mixture by dry way as according to the technologies "Dry-laid" or their mixture in suspension in wet water as in "wet-laid" (wet) technologies. The substrate can be obtained, for example, by means of an aqueous suspension in any proportion of natural and / or synthetic fibers. These fibers once suspended are preferably refined and supplemented with adjuvants well known to those skilled in the art for their implementation. In particular, defoamers, retention agents, binders, pigments, mineral fillers, wet strength agents and tackifiers can be used. This fibrous mixture can then be drained onto a web to result in the formation of the expected fibrous substrate which is then dried prior to being treated in accordance with the invention, in line.

EXTERNAL LAYER

According to another embodiment of the invention, the security sheet may further comprise an outer layer.

This outer layer, applied on at least one side of a sheet, is well known to those skilled in the art and allows, for example to enhance the durability properties of the sheet. The composition of such a layer is for example described in the application EP 1 319 104 .

The outer layer is initially, preferably, a preparation in aqueous phase, in particular an emulsion or a dispersion.

The external printability layer is preferably based on polyurethane.

The polyurethane is preferably applied as an aqueous dispersion of polyurethane or pro-polyurethane particles.

The polyurethane may be present in the composition intended to form the outer layer in a mass content of between 40 and 100% relative to the total weight of the composition.

The composition intended to form the outer layer may comprise a crosslinking agent chosen from isocyanates, carbodiimides or aziridines. The crosslinking agent may be in a mass content, by dry weight, of between 1 and 15%, better still 1 to 3%, relative to the total weight of the composition before coating.

The composition intended to form the outer layer also preferably comprises a mineral filler chosen from silica, kaolin, talc or calcium carbonate.

The composition intended to form the outer layer also preferably comprises a filler in a mass proportion by dry weight of between 1 and 60%, more preferably 3 and 10%, relative to the total weight of the composition.

PROCESS

1. (i) l'imprégnation dudit substrat avec une solution aqueuse d'un liant polymérique hydroxylé notamment en une proportion variant de 1 à 10 % en poids sec par rapport au poids des fibres en sec,
2. (ii) l'imprégnation dudit substrat avec une solution aqueuse d'au moins un dérivé silanol, et
3. (iii) le séchage du substrat modifié selon les étapes (i) et (ii),

As can be seen from the foregoing, the paper sheet according to the invention can be obtained according to the method comprising

1. (i) impregnating said substrate with an aqueous solution of a hydroxyl polymeric binder, especially in a proportion ranging from 1 to 10% by dry weight relative to the weight of the dry fibers,
2. (ii) impregnating said substrate with an aqueous solution of at least one silanol derivative, and
3. (iii) drying the modified substrate according to steps (i) and (ii),

step (ii) can be performed beforehand, simultaneously or consecutively to step (i).

Preferably step (ii) is performed simultaneously and / or consecutively in step (i).

In the latter alternative, the word "and" means that the substrate can undergo a 1 ^st impregnation with an aqueous solution of a hydroxylated polymeric binder and at least one silanol derivative and a 2 ^nd impregnation with only an aqueous solution at least one silanol derivative.

If the steps are consecutive, an additional drying step is performed between steps (i) and (ii).

silanol

As detailed below, the silanols can be of monopodal or dipodal type.

By "monopodal silanol" is meant a silanol which comprises only one silicon atom, the latter being bonded to at least one hydroxyl group.

By "dipodal silanol" is meant a silanol which comprises two silicon atoms, each bonded to at least one hydroxyl group.

The monopodal silanols that may be used according to the invention may or may not be obtained beforehand by a hydrolysis reaction of a corresponding alkoxysilane. This reaction is within the skill of those skilled in the art.

Advantageously, the alkoxysilanes used in hydrolysis reactions to provide monopodal silanols for the purposes of the invention are trialkoxysilanes.

Similarly, the synthesis of dipodal silanols is within the skill of those skilled in the art.

dans laquelle - A représente un groupement hydrocarboné divalent, saturé ou non, la chaîne hydrocarbonée peut être le cas échéant interrompue par un ou plusieurs atome(s) d'azote, d'oxygène, de soufre ou de phosphore, et substituée par un ou plusieurs groupements(s) hydrocarboné(s) comprenant un ou plusieurs atome(s) d'azote, d'oxygène, de soufre, de phosphore et d'halogène en particulier de fluor et/ou par un ou plusieurs groupement(s) cyclique(s) hydrocarbonées et dont la chaîne hydrocarbonée peut être le cas échéant interrompue par un ou plusieurs atome(s) d'azote, d'oxygène de soufre ou de phosphore,According to a first variant embodiment of the invention, the substrate may be brought into contact with a silanol derivative of formula (III):

in which - A represents a divalent hydrocarbon group, saturated or not, the hydrocarbon chain may be optionally interrupted by one or more nitrogen, oxygen, sulfur or phosphorus atom (s), and substituted by one or more a plurality of hydrocarbon groups comprising one or more nitrogen, oxygen, sulfur, phosphorus and halogen atoms, in particular fluorine, and / or one or more cyclic group (s) (s) hydrocarbon and whose hydrocarbon chain may be optionally interrupted by one or more nitrogen atom (s), sulfur or phosphorus oxygen,

Advantageously, the A-R unit is inert with respect to the fibers and the associated polymeric binder.

On the other hand, when the silanol is obtained according to a hydrolysis reaction of an alkoxysilane, preferably the A-R unit present on the alkoxysilane is such that it does not prove to be detrimental to the hydrolysis reaction. Thus sterically hindered and / or highly hydrophobic A-R units are to be avoided.

The taking into account of these requirements is clearly within the competence of those skilled in the art.

In this embodiment, the paper sheet obtained according to the invention comprises siloxane derivatives of formula (I) as previously represented, in which B is a bond -O- □ and R is a hydrogen or fluorine atom.

avec

• A tel que défini ci-dessus,
• G1 figurant un groupement fonctionnel réactif selon une réaction de couplage covalent, et
• G2 figurant un groupement fonctionnel complémentaire du groupement G1 au regard de la réaction de couplage considérée.

According to a second variant embodiment of the invention, the substrate may be brought into contact with two silanol derivatives of formula (IV) and (V):

with

• As defined above,
• G1 being a reactive functional group according to a covalent coupling reaction, and
• G2 appearing a complementary functional group of the group G1 with regard to the coupling reaction considered.

The groups G 1 and G 2 can for example be of amino, epoxy, sulphide, mercapto, methacryl, vinyl, ureido or fluorine type.

The skilled person is able to select G1 and G2 so that they react together.

For example, the substrate may be contacted with a silanol derivative having as G1 an epoxide group and a silanol derivative having as G2 an amine group.

In this embodiment, the sheet of paper obtained according to the invention comprises siloxane derivatives of formula (I) as previously represented, in which B and B 'are -O- □ bonds and R is a unit of formula (II). ) as previously shown.

According to a third variant embodiment of the invention, the substrate may be brought into contact with two silanol derivatives of formula (IV) and (V), with G1 and G2 respectively representing a reactive functional group according to a covalent coupling reaction but no not being complementary to one another, in the presence, simultaneous or not, of an auxiliary compound bearing two functional groups reactive according to a covalent coupling reaction and complementary to G1 and G2, respectively.

Those skilled in the art are able to select G1, G2 and the ancillary compound so that they react together as described above.

For example, the substrate may be brought into contact with silanol derivatives comprising, as G1 and G2, an epoxide group and a derivative comprising two terminal amine groups.

In this embodiment, the paper sheet according to the invention comprises siloxane derivatives of formula (I) as previously represented, in which B and B 'are -O- □ bonds and R is a unit of formula (II) as shown previously.

dans laquelle A peut par exemple être une entité dérivant d'un polyéthylène glycol tel que le diéthylène glycol, triéthylène glycol, tétraéthylène glycol, pentaéthylène glycol, hexaéthylène glycol, un polypropylène glycol tel que le dipropylène glycol ou tripropylène glycol, triéthylène glycol diamine, 2,2'-oxy(biséthylamine) ou tétraéthylène glycol amine.According to a fourth variant embodiment of the invention, the substrate may be brought into contact with a dipodal-type silanol derivative of formula (VI) so as to create a flexible bridge between fibers:

in which A may for example be an entity derived from a polyethylene glycol such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, a polypropylene glycol such as dipropylene glycol or tripropylene glycol, triethylene glycol diamine, 2 , 2'-oxy (bisethylamine) or tetraethylene glycol amine.

As compounds that can be considered to form the entity A, may be mentioned in particular the commercial derivatives Jeffamine D-230® (marketed by Huntsman) and Jeffamine D-400® (marketed by Huntsman).

In this embodiment, the paper according to the invention comprises siloxane derivatives of formula (I) as previously represented, in which R is a unit of formula (II) as previously represented.

The monopodal silanols that may be used according to the invention may or may not be obtained beforehand by a hydrolysis reaction of a corresponding alkoxysilane. This reaction is within the skill of those skilled in the art.

• le vinyltriéthoxysilane notamment celui commercialisé par Momentive (référence Silquest A-151NT),
• le γ-aminopropyltriéthoxysilane notamment celui commercialisé par Momentive (référence Silquest A-1100 silane),
• l'octyltriéthoxysilane notamment celui commercialisé par Momentive (référence Silquest A-137 silane),
• le γ-glycidyloxypropyl-triméthoxysilane notamment celui commercialisé par Struktol (référence SCA 960).

By way of illustrative and nonlimiting examples of alkoxysilanes, mention may be made of:

• vinyltriethoxysilane, in particular that marketed by Momentive (reference Silquest A-151NT),
• γ-aminopropyltriethoxysilane, especially that marketed by Momentive (reference Silquest A-1100 silane),
• octyltriethoxysilane, in particular that marketed by Momentive (reference Silquest A-137 silane),
• γ-glycidyloxypropyltrimethoxysilane, especially that marketed by Struktol (reference SCA 960).

However, certain silanols are also commercially available, for example hydrolyzed fluoroalkyl-triethoxysilane, in particular that marketed by Degussa (reference Dynasylan® F 8815).

The compounds referenced Dynasylan ^® SIVO 110, Dynasylan ^® SIVO 121 and Dynasylan ^® SIVO 160 marketed by Evonik can also be considered.

The silanols and alkoxysilanes marketed by Gelest Inc. and selected from those referenced in the "Silane Coupling Agents" brochure available from the address http://www.gelest.com/gelest/forms/GeneralPages/literature.aspx may also be in particular SILICLAD ^® , SIT 8378.5, SIC 2263.0, SIS 6984.0 and SIT 8378.3.

The step (ii) of impregnating said substrate with at least one silanol derivative is carried out with an aqueous solution of at least one silanol derivative.

The silanol derivative (s) are used in a proportion greater than 0.5%, preferably ranging from 5 to 30%, preferably from 10 to 20% by dry weight relative to the total weight of the fibers in dry form. .

Indeed, from a proportion of 0.5% of silanol derivative, in dry weight relative to the total weight of the fibers in dry, the insolubilization of the hydroxylated polymer is already noted.

A silanol may for example be dissolved in water at a level of more than 0.5%, preferably between 5% and 50% and more preferably between 10% and 50% by weight, preferably between 15% and 40%, before impregnation of the paper substrate.

As previously stated, the silanol (s) in question (s) can be contacted simultaneously or not with said hydroxylated polymeric binder with the fibrous substrate.

As regards the impregnation operation, it can be carried out by dipping, that is to say, immersion of the fibrous substrate in an aqueous bath containing at least one silanol derivative and said hydroxylated polymeric binder, or in two consecutive baths containing respectively at least said hydroxyl polymeric binder and a silanol derivative. In this embodiment, the one or more aqueous solutions are contacted with the fibrous substrate via an on-line impregnator.

This impregnation can also be achieved via the implementation of devices usually considered for surfacing, gluing or coating the paper. In this embodiment, the aqueous solution (s) are deposited on the surface of the fibrous substrate by means of an in-line surfacing, gluing or coating device, comprising in particular predose rollers, engraved rollers, transfer rollers before dosing. output. Said surfacing, sizing or coating device is preferably a size-press or a coater. It is more preferably a press-gluing machine to promote a "heart" impregnation.

In addition, this impregnation can be carried out by spraying.

According to a variant of the invention, the impregnation steps (i) and (ii) are carried out independently of one another by dipping, surfacing, sizing, spraying or coating.

According to a preferred embodiment of the invention, the impregnation steps (i) and (ii) are carried out simultaneously and by dipping.

The process according to the invention is particularly advantageous insofar as it makes it possible to incorporate silanol via a conventional method of manufacturing a sheet of paper, that is to say concomitantly with the conventional manufacturing steps.

It therefore advantageously requires no additional step other than those required for the manufacture of the paper sheet.

As previously described, the inventors have furthermore found that the use of silanol makes it possible to dispense with the insolubilizer usually required with regard to the hydroxylated polymeric binder.

Thus, in the process as described above for producing a sheet of paper, the silanol is furthermore used as the insolubilizing agent of said hydroxylated polymeric binder.

The drying of the substrate thus treated can be carried out for example by hot air or infrared, possibly seconded by driving rollers.

The surface temperature reached will be at least 30 ° C and at most 180 ° C, and this in relation to the residence time of the coated paper in the heating unit.

More specifically, the fibrous substrate is for example passed through a drying section formed of steam heated cylinders contacted with both sides of the fibrous substrate, or subjected to infrared radiation, or passed through a tunnel blowing hot air through the fibrous substrate.

The drying can be carried out at a temperature ranging from 50 to 250 ° C., in particular from 60 to 150 ° C.

The water is for example evaporated to a content ranging from 4 to 6% by weight in the finished fibrous substrate.

This drying step is also conducive to the crosslinking of the silanol derivatives with each other and / or with the hydroxyl groups of the fibrous substrate and / or the hydroxylated polymeric binder due to the dehydration conditions.

EXAMPLES

The examples given below are presented for illustrative and non-limiting purposes of the invention.

Measurement methods Resilience :

This measurement is carried out at 23 ° C and 50% humidity on a sample of 10cm x 2.5cm. It allows to visualize "the nervousness or spring effect" of the treated paper. The sample is folded on itself, without marking the fold beforehand, under the action of a weight of 2 kg for 30s. The weight is then removed and a reading of the resilience angle is performed after 30s. The more "nerve" the paper, the greater the angle of resilience, the less the crease will be marked.

The figure 1 in the appendix provides an illustration of this measure.

Folding rate:

The apparatus considered in the examples below to carry out the creasing prior to this measurement is that described by the NATIONAL OFFICE OF STANDARDS (CARSON, FT, SHAW, MB, Wearing quality of experimental currency type papers, J. Research NBS 36, 256-257 (1946) RP 1701 ).

1. a) un dispositif pour rouler l'éprouvette de papier en un cylindre. Ce dispositif est constitué d'un manchon fendu à l'intérieur duquel est placée une fourche mobile à deux dents,
2. b) un tube dont l'une des extrémités est pourvue d'un couvercle mobile,
3. c) un guide cylindre glissant à l'intérieur dudit tube,
4. d) un guide cylindrique permettant de maintenir à l'intérieur et en position verticale ledit piston dont la base inférieure repose à l'extrémité d'un levier. Le guide cylindrique est conçu de telle manière que le tube peut coulisser entre ledit guide et le piston,
5. e) un levier monté sur un pivot, et
6. f) un poids à l'extrémité du bras long dudit levier, opposée à celle du bras court qui supporte le piston.

He understands :

1. a) a device for rolling the paper test specimen into a cylinder. This device consists of a split sleeve inside which is placed a movable fork with two teeth,
2. (b) a tube with one end provided with a movable lid,
3. c) a sliding cylinder guide inside said tube,
4. d) a cylindrical guide for maintaining inside and in vertical position said piston whose lower base rests at the end of a lever. The cylindrical guide is designed in such a way that the tube can slide between said guide and the piston,
5. e) a lever mounted on a pivot, and
6. f) a weight at the end of the long arm of said lever, opposite to that of the short arm which supports the piston.

The creasing force is adjusted by the weight position on the lever arm so that the pressure on the piston is 10kg / cm ² ± 0.1 kg / cm ² .

The different cylindrical tracks, namely, the guide, the tube and the piston must be able to slide freely and in particular slide under the weight. With the tube and the piston in place in the guide, the piston must fall or rise as one raises or lowers the weight at the end of the lever. In case of impediment, check that there is no foreign body and wipe these parts.

• éclairage de l'échantillon en lumière rasante avec une source Schott KL1500 LED (Source lumière froide LED, intensité maximale) équipé du guide et de la rampe de lumière fixée à 2cm du bord de l'échantillon.
• photographie de l'échantillon avec un appareil photo numérique Canon A1100 IS (Mode Macro, Noir et Blanc avec préréglage du niveau de blanc à la lumière tungstene, ISO 100, Resolution 3264x2448 pixels) placé à 28 cm à la verticale de l'échantillon.
• analyse automatique d'une zone de la photographie (centrée ; résolution 1800x1800 pixels) à l'aide du logiciel Image J 1.43. L'analyse est effectuée par le lancement du programme basé sur le calcul du ratio (%) de pixels représentant les « creux » (noirs) et les « bosses » (blancs). Les différentes étapes du programme sont :
  • ✔ conversion de l'image (1800x1800 pixels) en 8 bit correspondant à 256 niveaux de gris,
  • ✔ opération de seuillage simple (ou binarisation) à 64. Ceci consiste à mettre à zéro tous les pixels ayant un niveau de gris inférieur à 64 et à la valeur maximale les pixels ayant une valeur supérieure. Ainsi le résultat du seuillage est une image binaire contenant des pixels noirs et blancs,
  • ✔ calcul du ratio pixels noirs / pixels blancs sur la totalité de l'image (1800x1800 pixels) correspondant au pourcentage de creux (% creux).

A square sample of 6.7 cm x 6.7 cm is crimped 8 times using the above-mentioned apparatus. It is then extracted from the device and then held at the four corners. The analysis of four images (rotation of the sample ¼ turn) high resolution of the sample via software allows to express the average rate of folds present on the analyzed surface. This analysis is done in three steps:

• sample illumination in grazing light with a Schott KL1500 LED source (LED cold light source, maximum intensity) equipped with guide and light bar fixed at 2cm from the edge of the sample.
• Sample photograph with a Canon A1100 IS digital camera (Macro Mode, Black and White with white level preset to tungsten light, ISO 100, Resolution 3264x2448 pixels) placed 28 cm vertically from the sample.
• automatic analysis of a photograph area (centered, 1800x1800 pixels resolution) using Image J 1.43 software. The analysis is performed by launching the program based on the calculation of the ratio (%) of pixels representing the "hollows" (black) and the "bumps" (white). The different stages of the program are:
  • ✔ conversion of the image (1800x1800 pixels) into 8 bit corresponding to 256 gray levels,
  • ✔ simple thresholding (or binarization) operation at 64. This consists of zeroing all the pixels having a gray level lower than 64 and the maximum value the pixels having a higher value. So the result of the thresholding is a binary image containing black and white pixels,
  • ✔ calculation of the ratio black pixels / white pixels on the whole image (1800x1800 pixels) corresponding to the percentage of hollow (% hollow).

An illustration of this measure is in particular in Example 5 below.

The water absoiption:

Measurements are made according to ISO 535 "Paper and board - Determination of water absorption, Cobb method".

Solubilization of PVA:

Five 5 cm x 5 cm squares of paper are weighed to the nearest milligram and cut into pieces and placed in a 250-mL Erlenmeyer flask sealed with 100 mL of distilled water.

The Erlenmeyer flask is closed and then placed in a water bath at 50 ° C. for 45 minutes with magnetic stirring.

The extract is then filtered in a filter crucible of porosity No. 1 and then diluted in a volumetric flask of 200 ml. A test portion of 20 mL is taken, to which 15 mL of boric acid at a concentration of 40 g / L and 3 mL of an iodine solution made by mixing 25 g of potassium iodide ( KI) and 12.7 g of diiodine (I ₂ ) in one liter of distilled water in a 50 ml volumetric flask. The green color obtained as a result of the chemical reaction makes it possible, via spectrophotometric analysis at 690 nm, to perform a quantization using a calibration curve.

This method is more precisely described in the publication Joseph H's Spectrophotometric Determination of Polyvinyl Alcohol in Paper Coatings .

Finley (review "Analytical Chemistry, December 1961, Volume 33, Number 13, pages 1925-1927 ), and in particular in the paragraph "Procedure" page 1925 .

The dry tensile strength and the wet tensile strength:

The measurements are carried out according to ISO 1924-2 "Paper and board - Determination of tensile properties - Part 2: Constant elongation gradient method (20 mm / min)".

Example 1

In this example, a series (series 1) of 4 paper samples (1A, 1B, 1C and 1D) having undergone standard processing was compared to a series (series 2) of these same papers (2A, 2B, 2C and 2D) functionalized with γ-glycidyloxypropyl-trimethoxysilane (marketed by Struktol under the reference SCA 960) hydrolysed (silanol derivative).

Type of paper and method of production:

In this example, the different types of paper are called A, B, C, and D.

Paper A consists of cellulosic fibers (100% cotton fibers). (samples 1A and 2A)

Paper B is made of cellulosic fibers and 10% of latex based on the weight of the fibers, it is prepared according to the patent FR 2 916 768 . (samples 1B and 2B)

Paper C is made of 90% cotton cellulosic fibers and 10% polyamide 6-6 synthetic fibers. (samples 1C and 2C)

The paper D is made of 90% of cellulosic cotton fibers, 10% of synthetic polyamide 6-6 fibers and 10% of latex based on the total weight of the fibers, it is prepared according to the patent FR 2 916 768 . (1D and 2D samples)

The substrate may comprise adjuvants known to those skilled in the art and commonly used in the paper industry, including retention agents and wet strength.

Operating mode:

The γ-glycidyloxypropyltrimethoxysilane was first hydrolysed as follows: in a beaker containing the alkoxysilane with magnetic stirring is added a mixture of water and acetic acid so as to adjust the pH to 3, 5. The solution is stirred for 15 minutes.

As a remark, those skilled in the art will adapt the time and the hydrolysis conditions according to the silane to be hydrolysed.

• chaque échantillon est plongé dans un premier bain, séché à 110°C pendant 10 minutes, puis immergé dans un second bain,
• pour les échantillons de la série 1 (non conforme à l'invention), le 1^er bain est standard (c'est-à-dire dénué de γ-glycidyloxypropyl-triméthoxysilane hydrolysé). Il contient de l'alcool polyvinylique (PVA), de la glycérine et de l'eau,
• pour les échantillons de la série 2 (conforme à l'invention), le 1^er bain est complémenté par une solution aqueuse de γ-glycidyloxypropyl-triméthoxysilane hydrolysé,
• pour les 2 séries, le 2^ème bain est standard, et contient du PVA, un agent de collage, de la glycérine, un agent insolubilisant et de l'eau,
• les papiers traités sont ensuite séchés à 110°C pendant 10 minutes.

The protocol chosen for the treatment of the papers detailed below is the following:

• each sample is immersed in a first bath, dried at 110 ° C. for 10 minutes, then immersed in a second bath,
• for the samples of Series 1 (not according to the invention), the bath ¹ is standard (that is to say devoid of hydrolyzed γ-glycidyloxypropyl-trimethoxysilane). It contains polyvinyl alcohol (PVA), glycerin and water,
• for samples of the series 2 (according to the invention), ¹ bath is supplemented with an aqueous solution of hydrolyzed γ-glycidyloxypropyl-trimethoxysilane,
• for the 2 series, the ^2nd bath is standard, and contains PVA, a bonding agent, glycerine, an insolubilizing agent and water,
• the treated papers are then dried at 110 ° C for 10 minutes.

• les composés présents dans les bains aqueux d'imprégnation, et
• la reprise sèche de chaque échantillon (différence de poids par unité de surface entre l'échantillon après et avant imprégnation sans tenir compte de l'eau).
  

The following table 1 provides information on:

• the compounds present in the aqueous impregnation baths, and
• the dry recovery of each sample (difference in weight per unit area between the sample after and before impregnation without taking into account the water).
  

a) Each of the samples thus obtained is characterized in terms of:

• water absorption (weight of water absorbed by the sample per unit area),
• deposition of silanol, that is to say of weight of silanol grafted onto the sample per unit area (calculated by multiplying the dry recovery by the dry silanol content in the composition of the impregnation bath),
• resilience,
• and fold rates.

The results obtained are reported in the following Table 2. <b> Table 2 </ b> Sample Removal (g / m ² ) Water Absorption or Cobb (g / m ² ) Fold rate (% hollow) Resilience (°) 1A 0 24 44 25 2A 8 18 40 65 1B 0 18 45 31 2B 6 14 32 61 1 C 0 23 47 32 2C 10 18 33 78 1D 0 17 41 40 2D 8 13 31 90

It can also be noted that the use of silanol in conjunction with PVA results in a significant decrease in the fold rate for all the samples (from 9 to 30%) and an increase in the resilience (from 97 to 160%). .

On the other hand, the papers thus obtained have hydrophobic properties since the water absorption has decreased for all the samples in a comparable manner according to the nature of the paper (from 22 to 25%).

b) In parallel, the mechanical properties have been characterized as follows:

The wet tensile strength and the dry tensile strength were thus measured on the 8 samples. The wet strength (ReH) is equal to the ratio of the wet tensile strength to the dry tensile strength.

The presence of silanol in the PVA bath affects little the dry traction of the samples (variations between 2 and 12%).

On the other hand, since the water absorption decreased in the presence of silanol in the PVA bath, the wet tensile strength increases significantly for the series 2 samples (from 16 to 25%).

As a result, the wet strength is improved for all of the Series 2 samples (from 12 to 21%).

In conclusion, the security documents according to the invention have hydrophobic properties, resilience and crease resistance, without the mechanical properties of said documents being altered. As regards more particularly wet strength, it is even improved for the security documents according to the invention.

Example 2

This example was carried out on paper C as defined in Example 1.

The silanol used was obtained as in Example 1, by hydrolysis of γ-glycidyloxypropyl-trimethoxysilane (reference SCA 960 marketed by Struktol) according to the procedure of Example 1.

In contrast, the treatment with silanol and PVA is carried out this time in 2 distinct steps. Indeed, the paper C was first brought into contact with the silanol by coating before impregnation in the two PVA baths of the series 1 of Example 1. The drying steps are carried out under the same conditions as in Example 1

Removal, resilience and fold rate were measured after treatment.

The results obtained are reported in the following Table 3. Similarly, the results of the sample 2C from Example 1 appear for comparison. The only difference between Example 2 and Sample 2C of Example 1 lies in the functionalization mode. Indeed, sample 2C had been functionalized by impregnation. <b> Table 3 </ b> Sample Removal (g / m ² ) Fold rate (% hollow) Resilience (°) Witness 0 47 35 Example 2 11 35 66 2C 10 33 78

Expected improvements in pleat rate and resilience are observed to a lesser degree than those achieved when the paper is impregnated, but remain very satisfactory in comparison with the values obtained with the control.

Example 3

• le papier utilisé est le D, tel que défini dans l'exemple 1,
• le couchage du silanol a été effectué après imprégnation dans les deux bains PVA de la série 1 de l'exemple 1.

Les mesures de dépose, résilience et taux de plis sont reportées dans le tableau 4 suivant. De même, les résultats de l'échantillon 2D provenant de l'exemple 1 apparaissent à titre comparatif. La seule différence entre l'exemple 3 et l'échantillon 2D de l'exemple 1 réside dans le fait que l'échantillon 2D avait été fonctionnalisé par imprégnation. Tableau 4 Echantillon Dépose (g/m²) Taux de plis (% creux) Résilience (°) Cobb (g/m²) Témoin 0 41 45 20 Exemple 3 15 33 82 6 2D 8 31 90 13 This example differs from Example 2 in that:

• the paper used is D, as defined in Example 1,
• the silanol coating was carried out after impregnation in the two series 1 PVA baths of Example 1.

Removal measures, resilience and fold rates are reported in the following Table 4. Similarly, the results of the 2D sample from Example 1 appear for comparison. The only difference between Example 3 and the 2D sample of Example 1 is that the 2D sample was functionalized by impregnation. <b> Table 4 </ b> Sample Removal (g / m ² ) Fold rate (% hollow) Resilience (°) Cobb (g / m ² ) Witness 0 41 45 20 Example 3 15 33 82 6 2D 8 31 90 13

Expected improvements in pleat rate and resilience are observed to a lesser degree than those achieved when the paper is impregnated, but remain very satisfactory in comparison with the values obtained with the control.

On the other hand, the papers obtained according to Example 3 have hydrophobic properties since the water absorption has decreased by 70% compared to the control.

Example 4

This example differs from Example 3 only in the silanol used for functionalization. Indeed in this example the silanol used and the SIVO 160 from Evonik Degussa.

A variant 4bis of this example was produced without insolubilization agent or bonding agent in the ^2nd bath of series 1 of Example 1.

The measures of removal, resilience, Cobb, fold rate and solubilized PVA are reported in the following Table 5. Similarly, the results of Example 3 appear for comparison. <b> Table 5 </ b> Sample Removal (g / m ² ) Fold rate (% hollow) Resilience (°) Cobb (g / m ² ) PVA solubilized (mg / 100g of paper) Witness 0 41 45 20 771 Example 4 8 38 60 6 68 Example 4bis 8 38 60 6 68 Example 3 15 33 82 6 Not measured

Expected improvements in ply rate and resilience are observed to a lesser extent compared to those obtained when the paper is functionalized with the silanol obtained by hydrolysis of γ-glycidyloxypropyltrimethoxysilane but remain nevertheless very satisfactory with respect to the values obtained with the witness.

On the other hand, the papers obtained according to Example 4 have hydrophobic properties since the water absorption has decreased by 70% compared to the control.

Comparing the fold, resilience, Cobb and solubilized PVA values for the samples of Examples 4 (comprising besides silanol an insolubilizing agent and a sizing agent) and 4 bis (devoid of insolubilizing agent and bonding agent), it appears that it is possible to overcome the insolubilization agent and the bonding agent.

Furthermore, by comparing the values of PVA solubilized for the control sample and the sample of Example 4a, it appears that the silanol obtained by hydrolysis of γ-glycidyloxypropyltrimethoxysilane (used in Example 4a) exerts an effect of improved insolubilization compared to the polyamide-epichlorohydrin resin (PAE) (used in the control sample).

Example 5

• la référence 1D de l'exemple 1,
• le papier traité 2D de l'exemple 1.

This example represents a visualization of the measurement of the fold rate for two samples:

• reference 1D of example 1,
• the 2D treated paper of Example 1.

Table 6 shows the relationship between the fold rate measured according to the method explained above and the visual assessment of the samples after creasing according to the BNIP 07 90 standard. <b> Table 6 </ b> Samples Pictures Fold rate (% hollow) Reference Figure 2a 41% Treated paper Figure 2b 31%

It appears very clearly by looking at Figures 2a and 2b that the silanol functionalized paper has a greater wrinkling resistance than the unfunctionalized paper. This coincides with the measurements of the fold rate achieved.

Claims (15)

1. A sheet of paper which is highly resistant to creasing and folding, particularly for the production of banknotes, comprising a fibrous substrate thoroughly impregnated with at least one hydroxylated polymeric binder, characterized in that said binder and the fibres of said substrate are at least partially covalently bonded to at least one siloxane derivative.
2. A sheet of paper according to Claim 1, characterized in that said siloxane derivative corresponds to the following formula (I):

   

   in which:

   - □ represents a covalent bond with a fibre, another silicon atom or said hydroxylated polymeric binder.

   - A represents a divalent, saturated or unsaturated, hydrocarbon group, the hydrocarbon chain can be interrupted if appropriate by one or more atom(s) of nitrogen, oxygen, sulphur or phosphorus, and substituted by one or more hydrocarbon group(s) comprising one or more atom(s) of nitrogen, oxygen, sulphur, phosphorus and halogen, particularly fluorine, and/or by one or more cyclic C3 to C6 group(s) or aromatic(s), and wherein the hydrocarbon chain can be interrupted if appropriate by one or more atom(s) of nitrogen, oxygen or sulphur or phosphorus,

   - B represents

   - a -O- □ bond, or

   - a halogen, or

   - a saturated or unsaturated, linear or branched or cyclic hydrocarbon group, having or not having one or more cyclic group(s) and wherein the hydrocarbon chain can be interrupted by one or more atom(s) of nitrogen, oxygen or sulphur,

   - R represents

   - an atom of hydrogen,

   - an atom of halogen and preferably of fluorine, or

   - a unit of formula (II)

   

   in which B' represents

   - a -O- □ bond, or

   - a halogen, or

   - a saturated or unsaturated, linear or branched or cyclic hydrocarbon group, having or not having one or more cyclic group(s) and wherein the hydrocarbon chain can be interrupted by one or more atom(s) of nitrogen, oxygen or sulphur.
3. A sheet of paper according to Claim 1 or 2, characterized in that B represents a -O- □ bond and R represents an atom of hydrogen or of fluorine.
4. A sheet of paper according to any one of the preceding claims, characterized in that A represents a divalent, saturated or unsaturated, hydrocarbon group, in which the hydrocarbon chain can be interrupted by one or more atom(s) of oxygen and substituted if appropriate by an epoxide group.
5. A sheet of paper according to Claim 2, characterized in that R represents the unit of formula (II) as defined in Claim 2, and B and B' represent a -O- □ bond.
6. A sheet of paper according to any one of the preceding claims, characterized in that said hydroxylated polymeric binder is made from polyvinyl alcohol (PVA), starch, pullulan, polyhydroxy-alkyl-methacrylate, polyglycerol-monomethacrylate or polysaccharide, said binder preferably being PVA-based and said hydroxylated polymeric binder preferably being in a proportion varying from 1 to 10% by dry weight related to the total weight of dry fibres.
7. A sheet of paper according to any one of the preceding claims, characterized in that said fibres are cellulose fibres mixed with synthetic fibres.
8. A sheet of paper according to any one of the preceding claims, characterized by the fact that the fibrous substrate also comprises a flocculated latex, particularly in a proportion varying from 6 to 50% by weight related to the total weight of dry fibres, and preferably in a proportion of 10% by weight.
9. A sheet of paper according to any one of the preceding claims, characterized by the fact that the fibrous substrate includes one or more watermark(s) and/or one or more security element(s).
10. A sheet of paper according to any one of the preceding claims, characterized in that it is a security document and in particular a banknote.
11. A multilayered structure comprising a sheet of paper according to any one of the preceding claims.
12. A method of manufacturing a sheet of paper which is highly resistant to creasing and folding, particularly for the production of banknotes as described in any one of the preceding claims, from a fibrous substrate, comprising:

    (i) impregnation of said substrate with an aqueous solution of a hydroxylated polymeric binder, in particular in a proportion varying from 1 to 10% by dry weight related to the weight of dry fibres,

    (ii) impregnation of said substrate with an aqueous solution of at least one silanol derivative, and

    (iii) drying of the substrate modified according to steps (i) and (ii),

    in which step (ii) can be carried out ahead of step (i), or simultaneously with step (i) or following step (i).
13. A method of manufacturing a sheet of paper according to the preceding claim, characterized in that the silanol derivative(s) is/are used in a proportion varying from 5 to 30% and preferably 10 to 20% by dry weight related to the weight of dry fibres.
14. A method of manufacturing a sheet of paper according to Claim 12 or 13, characterized in that the impregnation steps (i) and (ii) are carried out independently of one another by soaking, surfacing, sizing, spraying or coating, but preferably said impregnation steps (i) and (ii) are carried out simultaneously by soaking.
15. Use of a silanol derivative, in the process of manufacturing a sheet of paper having high resistance to creasing as described in Claim 12, as agent for rendering said hydroxylated polymeric binder insoluble.

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